Marcus Hutter is a rare exception who specified his AGI in such unambiguous mathematical terms that he actually succeeded at realizing, after some discussion with SIAI personnel, that AIXI would kill off its users and seize control of its reward button.

Not sure that's true of Hutter's beliefs, but for historical reference I'll link to a 2003 mailing list post by Eliezer describing some harmful consequences of AIXI-tl. Hutter wasn't part of that discussion, though.